1. Field of the Invention
This invention relates to a position-orientation recognition device applicable to a variety of factory automations, and more specifically, to a compound position-orientation recognition device comprising a sensor for obtaining two-dimensional information and a sensor for obtaining three-dimensional information.
2. Description of the Prior Art
Sensing the position and shape of different target works with various sensors is frequently required in assembling and machining operations or the like in a manufacture line. A sensor capable of obtaining a two-dimensional image is generally used for measurement of the position of the target work on the whole. If a CCD camera is used, for instance, a comparatively wide visual field can easily be provided by properly selecting an optical system (a lens). On the other hand, a laser sensor is effectively used for three-dimensional measurement of the local position and shape of the target work.
Laser sensors can be easily attached to a wrist portion of a robot and can measure the position and shape or the like of details of the target work accurately and on the real time base by irradiating laser beams from very close quarters to the target work, when designed to take the output from the laser sensor in a robot controller. For that reason, a laser sensor is frequently mounted on a robot system or the like, permitting the application to extensive fields including are welding, sealing and measurement or the like, for instance.
The laser sensor is classified into a type to scan with a laser beam in the form of a spot beam and another type to project a slit beam. In use of either type of the laser sensor, it is necessary to irradiate the spot or slit beam onto a target work surface surely. If the target work is located at a fixed position with a certain degree of accuracy and further a position close to the fixed position is taught to the robot as an approach position in advance, then it is easy to produce a state where a spot beam or slit beam is ready to be irradiated onto the target work surface rapidly.
However, in many cases according to an application, the position of a target work may remain unknown because positioning is not carried out or the accuracy of positioning of the target work is not reliable. In such a case, it is not possible to start a main measurement (shape measurement, for instance) with the laser sensor until the target work is found by search with the spot light beam or slit beam of the laser beam as a probe, while moving the laser sensor with a transfer means such as a robot.
In general, laser sensors are not suitable for measurement in a wide area, taking a time for searching for the target work and subsequent approaching to the target work. According to the circumstances, it may be difficult to cause a laser sensor to search a target work surely.